1. Technical Field
The present invention relates to radar systems. More particularly, the present invention relates to transmit/receive modules in compact packages.
2. Description of the Background Art
A variety of technical problems face one looking to equip an airplane with Ku and Ka band radars (for simplicity, K band radars are referred to with lower case letters, not the official subscripts). Modern radars systems are often implemented as active electronically scanned arrays with hundreds of transmit/receive modules aligned in an array. One advantage of an active electronically scanned array is that it can perform radar scans without physically turning the radar array. This is accomplished by altering the phase of the transmitted radars. By synchronizing the phases of each of the transmit/receive modules, the beam transmitted points in a different direction. However, in order to change the direction of the radar beam (i.e., the main lobe) the transmitted radars must be packed close enough together to work in unison.
Ka band radar, short for “K above,” is transmitted at approximately 18-40 GHz. Because such high frequencies are being used, the transmit/receive modules must be packed very tightly. In an active electronically scanned array, the lattice spacing must be approximately half of the wavelength of the highest frequency used. Ka band radar requires five elements per inch. Systems operating in the X band, e.g. 10 GHz, had ten times as much area in which to place transmit/receive modules. The demanding space requirements were too small for the current size of transmit/receive modules.
In addition to the size of the modules, a designer must also contend with the size of the connections to and from modules. Prior art designs require bulky connectors connecting a module to a radiating element. Prior art designs also require a connector from the module to a manifold interconnect. The inventors discovered that current connectors did not meet the height requirements of a Ka band radar grid.
These issues are compounded where a plane needed both Ku and Ka band radars. The module must be small enough to be able to create an effective array of Ka band radar, but still make room for both Ka band radar technology and Ku band radar technology. Because these two bands are at different frequencies, they must be transmitted and received separately. At the same time, the circuitry for both must be compact enough that it can fit into the Ka space requirements.